The mechanism proposed by the authors is based on the assumption that fermented dairy products (which showed the opposite effects compared to non-fermented milk) is free of galactose. For most fermented dairy products, this is however not true. The paper quoted by the authors themselves (ref 15 in the paper), shows a decrease in lactose from 4.8 to 2.3 g/100g in yoghurt, with an increase in galactose of 1.3 g/100g. The loss of lactose thus equals 2.5 g/100g. As lactose is composed of glucose and galactose (which have equal molecular weight), this decrease in lactose would lead to 1.25g/100g of galactose formed, which is equal to the 1.3 g/100g in the quoted paper. This therefore shows that yoghurt leads to equal galactose intake as milk (and in lactase non-persistent consumer to even higher galactose intakes compared to intake of non-fermented milk).
For (semi)hard cheeses, there is a somewhat lower galactose intake, due to the washing of the curd during production, but also cheese is not generally free from galactose.
But overall, the galactose intake from fermented dairy (which in the paper focuses on soured milk and yoghurt) is equal to the galactose intake from regular dairy, therefore making this proposed mechanism highly unlikely.
Competing interests: No competing interests